Alexander Fügl

S-Nitroso Human Serum Albumin Treatment Reduces Ischemia/Reperfusion Injury in Skeletal Muscle via Nitric Oxide Release

Background—Peroxynitrite generated from nitric oxide (NO) and superoxide (O2−) contributes to ischemia/reperfusion (I/R) injury. Feedback inhibition of endothelial NO synthase by NO may inhibit O2− production generated also by endothelial NO synthase at diminished local l-arginine concentrations accompanying I/R. Methods and Results—During hindlimb I/R (2.5 hours/2 hours), in vivo NO was monitored continuously (porphyrinic sensor), and high-energy phosphates, reduced and oxidized glutathione (chromatography), and I/R injury were measured intermittently. Rabbits receiving human serum albumin (HSA) (controls) were compared with those receiving S-nitroso human serum albumin (S-NO-HSA) beginning 30 minutes before reperfusion for 1 hour or 30 minutes before ischemia for 3.5 hours (0.1 &mgr;mol · kg−1 · h− 1). The onset of ischemia led to a rapid increase of NO from its basal level (50±12 nmol/L) to 120±20 and 220±15 nmol/L in the control and S-NO-HSA–treated groups, respectively. In control animals, NO dropped below basal levels at the end of ischemia and to undetectable levels (<1 nmol/L) during reperfusion. In S-NO-HSA–treated animals, maximal NO levels never decreased below basal concentration and on reperfusion were 100±15 nmol/L (S-NO-HSA preischemia group, 175±15 nmol/L). NO supplementation by S-NO-HSA led to partial and in the preischemia group to total preservation of high-energy phosphates and glutathione status in reperfused muscle (eg, preischemia groups: ATP, 30.23±5.02 &mgr;mol/g versus control, 15.75±4.33 &mgr;mol/g, P <0.0005; % oxidized glutathione, 4.49± 1.87% versus control, 22.84±6.39%, P <0.0001). S-NO-HSA treatment in all groups led to protection from vasoconstriction and reduced edema formation after reperfusion (eg, preischemia groups: interfiber area, 12.94±1.36% versus control, 27.83±1.95%, P < 0.00001). Conclusions—Long-lasting release of NO by S-NO-HSA provides significant protection of skeletal muscle from I/R injury.

Impact of dietary vitamin D on osseointegration in the ovariectomized rat

AIM Vitamin D deficiency is highly prevalent in the population and associated with impaired peri-implant bone regeneration. Yet, there is a gap in understanding the impact of vitamin D supplementation on the process of osseointegration. In this study, the effect of vitamin D supplementation on peri-implant bone regeneration was investigated. METHODS Fifty ovariectomized Sprague-Dawley rats were divided into three groups. The depletion group was fed a vitamin D-free diet for 8 weeks. The repletion group received vitamin D-free diet for 6 weeks, before animals were switched to standard diet containing 2400 IU/kg vitamin D. The control group was fed the standard diet. Two titanium mini-implants were placed in the tibia. All groups remained on their previous diet until sacrifice. Blood sample testing and histomorphometric analysis were performed. RESULTS Vitamin D depletion caused a significant reduction in 25-hydroxvitamin D in rat serum that returned to control levels in the repletion group. This vitamin deficiency was associated with a decrease in bone-to-implant contact in the cortical area, which was leveled to controls in the repletion group. No significant changes by vitamin D depletion were noticed in the medullar compartment. Moreover, also the peri-implant bone area and the mineral apposition rate remained unchanged upon vitamin D depletion. CONCLUSION These results indicate that vitamin D deficiency has a negative impact on cortical peri-implant bone formation in ovariectomized rats, which can be compensated by vitamin D supplementation. This study provides first insight into the potential beneficial effect of vitamin D supplementation in implant dentistry.

Dimethyloxalylglycine lyophilized onto bone substitutes increase vessel area in rat calvarial defects.

AIM Pharmacological inhibitors of prolyl hydroxylases, also termed hypoxia-mimetic agents (HMAs), when repeatedly injected can support angiogenesis and bone regeneration. However, the possible role of HMA loaded onto bone substitutes to support angiogenesis and bone regeneration under diabetic condition is unknown. The capacity of HMA loaded onto deproteinized bovine bone mineral (DBBM) to support angiogenesis and bone formation was examined in diabetic Wistar rats. METHODS Diabetes was induced by intraperitoneal injection of streptozotocin. The HMA dimethyloxalylglycine (DMOG) and desferrioxamine (DFO) were lyophilized onto DBBM. Calvarial defects were created with a trephine drill and filled with the respective bone substitutes. After 4 weeks of healing, the animals were subjected to histological and histomorphometric analysis. RESULTS In this report, we provide evidence that DMOG loaded onto DBBM can support angiogenesis in vivo. Specifically, we show that DMOG increased the vessel area in the defect site to 2.4% ± 1.3% compared with controls 1.1% ± 0.48% (P = 0.012). There was a trend toward an increased vessel number in the defect site with 38.6 ± 17.4 and 31.0 ± 10.3 in the DMOG and the control group (P = 0.231). The increase in angiogenesis, however, did not translate into enhanced bone formation in the defect area with 9.2% ± 7.1% and 8.4% ± 5.6% in DMOG and control group, respectively. No significant changes were caused by DFO. CONCLUSIONS The results suggest that DMOG loaded onto DBBM can support angiogenesis, but bone formation does not increase accordingly in a type 1 diabetic rat calvarial defect model at the indicated time point.

S-nitroso albumin enhances bone formation in a rabbit calvaria model.

Nitric oxide (NO) is a mediator involved in bone regeneration. We therefore examined the effect of the novel NO donor, S-nitroso human serum albumin (S-NO-HSA) on bone formation in a rabbit calvaria augmentation model. Circular grooves (8 mm diameter, two per animal) were created by a trephine drill in the cortical bone of 40 rabbits and titanium caps were placed on the rabbit calvaria bone filled with a collagen sponge soaked with either 100 μL S-NO-HSA (5%, 20%) or human albumin (5%, 20%). After 4 weeks the titanium hemispheres were subjected to histological and histomorphometric analysis. Bone formation and the volume of the residual collagen sponge were evaluated. S-NO-HSA treatment groups had a significantly higher volume of newly formed bone underneath the titanium hemispheres compared to the albumin control groups (5%: 15.5 ± 4.0% versus 10.6 ± 2.9%; P < 0.05; 20%: 14.0 ± 4.6% versus 6.0 ± 3.8%; P < 0.01). The volume of residual collagen sponge was also significantly lower in the S-NO-HSA groups compared to the control groups (5%: 0.4 ± 0.5% versus 2.6 ± 2.4%; P < 0.05 and 20%: 1.5 ± 2.7% versus 13.0 ± 18.7%; P < 0.01). This study demonstrates for the first time that S-NO-HSA promotes bone formation by slow NO release. Additionally, S-NO-HSA increases collagen sponge degradation.

Bisphosphonat-assoziierte Osteonekrosen des Kieferknochens@@@Bisphosphonate-associated osteonecrosis of the jaw

SummaryIntravenous application of bisphosphonates (BP) represents an established therapeutic strategy of tumor-associated bone metastasis and severe hypercalcemia. Patients can develop osteonecrosis of the jaw (ONJ) as a side effect of this therapy. The diagnosis of ONJ is based on three criteria: a) patients have been or are currently treated with BP; b) a deficiency in wound healing, which is in 70–80% associated with necrotic alveolar bone, characteristically exposed, is present for at least 8 weeks and c) no radiotherapy of the head and neck was performed. The suppression of bone turnover, concomitant with high functional load of the alveolar bone, and the subsequent accumulation of microfractures are considered the main pathologic factors of this disease. The cumulative incidence of ONJ lies approximately between 1 and 10% in oncologic patients, being associated with the antiresorptive potency and the respective molecular structure of the BPs. Patients with multiple myeloma develop ONJ more frequently than patients with other oncological diseases such as metastasizing breast- and prostate cancer, a fact that may also be due to the higher transfusion/injection frequency of BP in these patients. Dental treatment strategies are responsible for the occurrence of ONJ in approximately 80% of cases. Based on a clinical staging, patients can be grouped into three categories and should receive the corresponding treatment regime. Prospective clinical studies are required for a better understanding of etiology and pathogenesis of ONJ to make treatment, risk estimation and prognosis of ONJ more accurate.ZusammenfassungDie intravenöse Verabreichung von Bisphosphonaten (BP) ist eine etablierte Basistherapie bei der Behandlung von Tumor-assoziierten Knochenmetastasen (osteoklastischen und osteoplastischen Metastasen) sowie schwerer Hyperkalzämien. Als unerwartete Komplikation dieser Behandlung wurde das Auftreten von Osteonekrosen im Kieferknochen (engl. BP-associated osteonecrosis of the jaw; ONJ) beschrieben. Die Diagnose der ONJ basiert auf drei Kriterien: a) die Patienten müssen mit BP behandelt worden sein; b) eine Wundheilungsstörung in der Mundhöhle, in 70–80% assoziiert mit einem exponierten, nekrotischen Kieferknochen, besteht länger als 8 Wochen und c) eine vorangegangene Radiotherapie des Kopf/Halsbereiches hat nicht stattgefunden. Die Pathogenese der ONJ steht im möglichen Zusammenhang mit der Akkumulation von Mikrofrakturen, die als Folge eines eingeschränkten Knochenumbaus, bei gleichzeitig hoher funktioneller Belastung des Kieferknochens, auftreten. Die kumulative Inzidenz der ONJ beträgt etwa 1 bis 10% bei Tumorpatienten, wobei ein Zusammenhang mit der antiresorptiven Potenz der einzelnen BP sowie deren Molekülstruktur besteht. Schon nach 2–3 Infusionen/Injektionen kann eine ONJ auftreten. Diese Komplikation tritt bei Patienten mit Multiplem Myelom häufiger auf als bei Patienten mit anderen onkologischen Grunderkrankungen, wie metastasiertem Mamma- oder Prostatakarzinom, was allerdings auch mit dem häufigeren Einsatz von BP bei Multiplem Myelom verbunden werden kann. Zahnärztliche Eingriffe sind in 80% auslösend für die Entstehung der ONJ. Patienten werden im Sinne eines klinischen Stagings in drei Kategorien eingeteilt und ein entsprechendes Behandlungskonzept angewandt. Weiterführende prospektive klinische Studien sind erforderlich, um die Ätiopathogenese besser zu verstehen und darauf aufbauend die Behandlungsstrategien zu optimieren und Risikofaktoren und Prognose besser abschätzen zu können.Intravenous application of bisphosphonates (BP) represents an established therapeutic strategy of tumor-associated bone metastasis and severe hypercalcemia. Patients can develop osteonecrosis of the jaw (ONJ) as a side effect of this therapy. The diagnosis of ONJ is based on three criteria: a) patients have been or are currently treated with BP; b) a deficiency in wound healing, which is in 70-80% associated with necrotic alveolar bone, characteristically exposed, is present for at least 8 weeks and c) no radiotherapy of the head and neck was performed. The suppression of bone turnover, concomitant with high functional load of the alveolar bone, and the subsequent accumulation of microfractures are considered the main pathologic factors of this disease. The cumulative incidence of ONJ lies approximately between 1 and 10% in oncologic patients, being associated with the antiresorptive potency and the respective molecular structure of the BPs. Patients with multiple myeloma develop ONJ more frequently than patients with other oncological diseases such as metastasizing breast- and prostate cancer, a fact that may also be due to the higher transfusion/injection frequency of BP in these patients. Dental treatment strategies are responsible for the occurrence of ONJ in approximately 80% of cases. Based on a clinical staging, patients can be grouped into three categories and should receive the corresponding treatment regime. Prospective clinical studies are required for a better understanding of etiology and pathogenesis of ONJ to make treatment, risk estimation and prognosis of ONJ more accurate.